"There are families of these criminal outlaws who know what's happened and who by their silence are putting other people at risk."

Senior police have joined the chorus of condemnation.

Deputy Commissioner Nick Kaldas, standing with the premier on Tuesday, said it was up to neighbours and others in Sydney's violence-ridden communities to help police fight gun crime.

"Evil prospers where good men choose to do nothing," Mr Kaldas said.

"Our community has a lot of good men and women who have chosen to do nothing, as the premier said, for quite some years.

"It's time for them to step up and say, 'I'm not going to tolerate this, I won't put up with it in my house, my street, my neighbour, and if I see something I will pick up the phone and let the police know'."

Commissioner Andrew Scipione said NSW Police had a good track record of protecting the anonymity of those who provided intelligence.

"Tell us where the guns are, who the shooters are, and we will do the rest," he said.

"You can rest assured we will protect you."

He said NSW Police were about to introduce new laws giving police more powers to stop, search, detain and arrest people suspected of having illegal firearms.

Mr O'Farrell defended the fact that no gang had yet been banned under the state's anti-bikie laws, saying the government wanted to make sure any action taken would stand up to a legal challenge.

"If we infringe (an) evidence-based approach, my advice is, the legislation will prove to be ineffective because it will be knocked out by the lawyers of these outlaw motorcycle gangs," he said.

Mr Kaldas said Brothers 4 Life could be more difficult to prohibit than other gangs because of its loose structure.

Mr O'Farrell said the government was working with the federal government on laws to allow the seizure of unexplained wealth, as well as plugging holes in "porous" federal borders to staunch the flow of guns into Australia.

The NSW Opposition accused the premier of allowing gun crime to spiral out of control.

"Barry O'Farrell's inaction on criminal gangs is allowing a culture of gun violence to grip Sydney's streets," Opposition Leader John Robertson said in a statement.